Electronic imaging has become a major field of development and large numbers of electronically generated images are being produced in many sectors of life, such as engineering, design, security and education. These images are created in a variety of different ways, for example by use of computer generating techniques or through reproduction of images detected by scanning devices. The development of scanning devices in particular has enabled large quantities of detailed image data to be formed.
Such electronically generated images can be stored as data files for future retrieval and manipulation. However, as the number of these images and the size of the databases holding the associated data files has increased problems have arisen in enabling a user to quickly and easily access and manipulate these data files.
Several prior art techniques exist for retrieving data representing stored images. One such system allows the user to append an alphanumeric identifier to data files at the time the data is stored thus enabling later access to the information. However, although these identifiers can be descriptive, difficulties can arise when accessing the file contents, particularly for a user who did not originally input the image data and does not know what the identifier is, or for a user who has simply forgotten what the identifier is. For a user in this situation the only option would be to examine the contents of each file, one by one, until the desired image has been located.
Improvements to the above system have been made, allowing the user to append several alphanumeric identifiers to the data file when it is stored in the database, instead of just one. Of these identifiers one would be the actual file name and the remaining would be descriptive keywords to facilitate searching for the file at a later date. The user can then search the database for a desired image by entering a selection of keywords which he considers to describe the image he wishes to retrieve. These keywords are used by the database system as search words, the data files stored therein being searched to see if they have any of those keywords appended to them. Once the database has been searched the user will then be presented with a list of file names representing those data files which had one or more of the selected keywords appended to them. From these file names the user can pick one or more for further manipulation or can perform further searching, if for example the list of file names is too large or if the desired data file is not present within the list. However a user may still face the same problem as above in that the file names may be meaningless to him, and he would then have to resort to looking at the corresponding images one by one.
"Turn-page" systems access image data, at the user's command, one page at a time. For example, a file may contain data pertaining to several images. In order for the user to access the correct image for subsequent data handling (e.g. sending to a printer), each page of the file is output sequentially to screen, and the user selects the correct image for printing. Such systems require that the full image data for each page be manipulated and presented on screen one page at a time; hence, a great deal of time is spent transferring superfluous data (that is pages of the file that the user does not want to print) through the system.
In European patent application EP 0,415,529 an information handling system is described in which data is input into the system, for example via a scanner, and is stored in an image store. Compression logic then reduces the data in the image store to form a scaled or iconic image of the original full image data, which is stored in bit map form in the system in association with data for the full image. The iconic image preserves the salient features of the full image but without retaining unnecessarily fine detail, and acts as a pictorial tag for the full image, replacing the file names of the earlier systems. If a user opens a file then iconic images associated with each full image contained within that file appear on the monitor screen together. This icon system can also be incorporated with systems that search on keywords as described above, the result of such a search being that a group of icons appears on the screen rather than a list of file names. The user can then select, for example using a mouse and a cursor, a particular iconic image and thus access the associated full image for viewing on the display. This approach has proved to be more advantageous than the other described techniques since identification is made by looking at a fixed reduced size image of the original and not from a file name which may not have a great deal of meaning to the user.
However the above approach of creating icons does have disadvantages. Since icons only contain the salient features of an original image, and none of the fine detail, they are rather coarse and so do not lend themselves to quality compression, particularly in color. Also the icons cannot be decompressed to produce a more detailed representation since they contain no information that would enable such decompression. Thus icons, once generated, are of a fixed size. This inflexibility means that, in general, a set of icons will not be ideal for display, there being either too many to enable all the icons within the set to be displayed at once, or at the other extreme there being only a few in which case a large proportion of the display area is left unused.